1. Field of the Invention
The present invention relates to a bistable member usable, for example, in a snap fastener assembly or a spring latch assembly. The present invention also relates to assemblies incorporating the bistable member.
2. Description of the Prior Art
Snap fasteners employing resilient dish-shaped or curved-disk-shaped members are disclosed, for example, in U.S. Pat. Nos. 4,099,303 and 3,769,664 (Parera), U.S. Pat. No. 3,538,557 (Hirose) and U.S. Pat. No. 2,816,340 (Domenech et al.). In each of these references, the dish-shaped member is mounted on a female portion of the fastener, and includes hooks or protrusions mounted on legs extending from the peripheral edge of the member. When a male portion of the fastener is aligned with and pushed against the female portion, the dish-shaped member biases the legs such that the hooks/protrusions engage, for example, a slot formed in the male portion. Subsequently, when the male portion is pushed toward the female portion, the dish-shaped member is inverted, thereby disengaging the hooks/protrusions from the slot and causing the legs to rotate away from the male portion. This allows the released male portion to be separated from the female portion.
A significant drawback to the above-mentioned fastener structures arises because the force used to release the fastener is applied in the same direction as the force used to latch the fastener. This creates confusion because it is often unclear when the male portion is disengaged and may be separated from the female portion. Specifically, because the male portion is not forced away from the female portion when the fastener is released, it is difficult to detect when the male portion may be separated from the female portion.
A fastener addressing the above mentioned drawback is disclosed in U.S. Pat. No. 5,189,768 (Riceman et al.). This reference teaches the use of a spring located between the male and female portions that pushes the disengaged male portion away from the female portion. However, this fastener structure includes an even more complicated structure to incorporate the spring. In addition, as with the above-mentioned fastener structures, the force used to release the fastener is applied in the same direction as the force used to latch the fastener. Therefore, an operator must push against the resilient force exerted by the spring during both the releasing and latching operations.
Spring latches are mechanisms including a resilient member (such as an elastic rubber strap, spring or bow) that is restrained and triggered by a latching device to eject or propel a projectile. Toys and devices which eject/propel an article using such spring latches have been popular for centuries (e.g., crossbows, catapults, etc.). The resilient member stores potential energy during a relatively slow, typically manual arming process, and then quickly releases the potential energy to eject/propel the projectile with high velocity upon triggering by the latching device. A principle drawback of these devices is that the latching device must have sufficient strength to support the potential energy stored in the deformed, and therefore unstable, resilient member. To provide adequate support, the latching device is often bulky or made of high-cost materials, thereby constituting a substantial portion of the total cost of the device.